The failure of axons to regenerate after a spinal cord injury (SCI) remains one of the greatest challenges in neuroscience. The initial mechanical trauma is followed by a secondary injury cascade, creating a hostile microenvironment, which not only is not permissive to regeneration but also leads to further damage. One of the most promising approaches for promoting axonal regeneration is to maintain the levels of cyclic adenosine monophosphate (cAMP), specifically by a phosphodiesterase-4 (PDE4) inhibitor expressed in neural tissues. Therefore, in our study, we evaluated the therapeutic effect of an FDA-approved PDE4 inhibitor, Roflumilast (Rof), in a thoracic contusion rat model. Results indicate that the treatment was effective in promoting functional recovery. Rof-treated animals showed improvements in both gross and fine motor function. Eight weeks post-injury, the animals significantly recovered by achieving occasional weight-supported plantar steps. Histological assessment revealed a significant decrease in cavity size, less reactive microglia, as well as higher axonal regeneration in treated animals. Molecular analysis revealed that IL-10 and IL-13 levels, as well as VEGF, were increased in the serum of Rof-treated animals. Overall, Roflumilast promotes functional recovery and supports neuroregeneration in a severe thoracic contusion injury model and may be important in SCI treatment.

Innovations in spinal cord injury (SCI) models are crucial for developing effective therapies. This study introduces a novel in vitro SCI model using cultures of primary mixed spinal cord cells from rat pups, featuring key spinal cord cell types. This model offers distinct advantages in terms of feasibility, reproducibility, and cost-effectiveness, requiring only basic cell culture equipment. Following hyperosmotic stress via sorbitol treatment, the model recapitulated SCI pathophysiological hallmarks, with a 65% reduction in cell viability and gradual cell death over 48 h, making it ideal for evaluating neuroprotective agents. Notably, the human adipose tissue stem cell (hASC) secretome provided significant protection: it preserved metabolic viability, reduced β amyloid precursor protein (β-APP) expression in surviving neurons, and modulated the shift in the astrocytic morphotype. A transcriptomic profile of the effect of the hASC secretome treatment showed significant functional enrichments related to cell proliferation and cycle progression pathways. In addition to supporting the use of the hASC secretome as a therapy for SCI, this study is the first to use sorbitol as a hyperosmolar stressor to recapitulate key aspects of SCI pathophysiology. Thereby, this model can be used as a promising platform for evaluating therapeutic agents targeting neuroprotection and neuroregeneration, offering outputs related to cell death, neuronal stress, and protection, as well as induction of glial reactivity.

Cell-free therapies based on the mesenchymal stem cells (MSCs) secretome are being widely explored for spinal cord injury (SCI). Induced pluripotent stem cells (iPSCs) provide a scalable source for generating mesenchymal stem cells (iMSCs), but limited studies have evaluated the modulatory capacity of iMSCs for CNS applications. Due to the importance of the glial and vascular responses to SCI progression, this study evaluated the activity of the iMSCs secretome on glial and endothelial cells in SCI-relevant paradigms. In primary mixed spinal cord cultures, the secretome was tested under supplement withdrawal and hyperosmotic injury conditions, while endothelial network formation was assessed in a morphogenesis assay. In vitro, the iMSCs secretome promoted a modest protective effect on cell survival, modulated astrocyte morphology and preserved myelin basic protein expression within the oligodendroglial lineage, without clear alterations in microglial morphometric readouts. Secretome treatment also increased Arg1 expression in mixed spinal cord cultures. In endothelial cultures, the secretome promoted a denser and more interconnected endothelial network. In a mouse thoracic SCI model, the secretome was administered intravenously, and tissue was analyzed one week after injury. In vivo, the secretome reduced perilesional GFAP coverage and increased selected vascular morphometric parameters without altering lesion size or microglia morphological readouts. Overall, these findings indicate that the iMSCs secretome produced context-dependent changes in glial and vascular cells, mainly regarding morphological parameters, supporting further studies of iPSC-derived MSCs as a scalable source for secretome-based strategies.